That's a nice old amp, Matt. I wouldn't worry about the tubes. The Svetlana tubes are well-built and should power right up. That said, it's probably not a bad idea to cook them with filament and HV,(
Hi Matt, I dont think youve got anything to worry about, even with -160V, either with 811As or 572Bs. Both tubes are routinely run with -200V in Class C, so since you just want them to be cut off, I
I agree with Bill. Theres no problem grounding the CT of the filament xfmr (and bypassing the fil leads at the tube socket), but I prefer keeping the cathode isolated, and dedicated to the B- return.
About fifteen years ago, I rebuilt a junker Alpha 76 (no tubes, flashed-over bandswitch, burned plates on tuning cap, burned plate choke, other problems) and converted it to a six meter monoband ampl
Thats abnormal behavior for an 8877, Conrad, and its interesting your friend hasnt seen the negative grid current with other tubes. Otherwise, id speculate the problem was a measurement artifact, cau
Thanks, everybody, for weighing in on comments, re my request for advice about 6m parasitic suppressors. The near-consensus viewpoint was that no suppressors were needed for the 3CX800A7 in the ampli
Sounds like a corona discharge, which suggests the HV is still on or the filter cap isnt fully discharged. Time to be very cautious until you figure it out. 73, Jim w8zr Sent from my iPhone _________
I prefer method 1, except I'd ground the CT of the film xfmr, while also bypassing the fil leads. For an 8877, I drive don't see any need to couple the cathode to the fil. The lack of bifilar fil cho
I agree, Jim. Either way works fine. Re arcing from cathode to filament: I dont see why the cathode voltage would ever soar above the tubes cutoff bias, which in my 8877 amps is about 28V. An interna
Gary, I doubt you will find a drop-in replacement blower for the original rotron blower in your amplifier. It's a wonderful blower, and extremely reliable, but hasn't been made for years. Mine is thi
Herb, that's usually a sign of no plate voltage on the tube. 73, Jim w8zr Sent from my iPhone _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contes
Jim, I'd connect it to neutral, which would provide the most protection for your equipment. Since N and G are bonded at the 200A service entrance, there isn't a safety issue with N soaring above G. T
Jim, let me know if you still need a knob and I'll drop one in the mail for you. It has a 3/8 hole, two set screws and is about 1.75" diameter. I believe it is new. In any case the price is right (fr
Jim, in digging a little deeper in my knob bin, I found a variac knob with a 3/8 inch hole, two set screws, 2-3/4 diameter. Same price (free) as other knob. Jim w8zr Sent from my iPhone _____________
I had a conversation with Nate, one of the sales reps for the new FlexRadio "PowerGenius XL" solid state 2000W (ICAS) amplifier. Unfortunately, I'm sorry to report that for CW operators such as mysel
Tnx for the info, Paul. Yes, in principle 7mS is fast enough, but the data sheet doesn't specify contact bounce which, for this type of relay typically adds another 4-7mS. Even vacuum relays (excepti
I agree mostly with Victor's comments, but would like to expound on a couple things about QSK and semi-QSK which appear to cause confusion. (1) Most modern transceivers have provisions for delaying R
A well-designed amplifier QSK circuit should never allow hot-switching of the amplifier's T/R relays under any circumstances. There are several ways to accomplish this goal, none of them expensive or
There has been considerable discussion on this group and elsewhere about the forthcoming FlexRadio Power Genius XL high-end solid state amplifier. Some of us, myself included, have wondered about th
My comments about the new Flex amplifier's CW behavior has morphed into a very interesting discussion about SDR vs. non-SDR transceivers and their suitability for QSK keying. (BTW, I should have said